Cryptographic performance for Rijndael and RC6 block ciphers

This paper deals with the cryptographic performance of Rijndael and RC6 algorithms in real environment. The cryptographic performance of Rijndael and RC6 algorithms is evaluated from the diffusion, confusion, and space-time complexity of them. The diffusion and confusion of them are quantitatively measured by using the avalanche effect and runs test. The time performance metrics are encryption and decryption speeds while space performance metric is memory utilization. The experimental results show that both Rijndael and RC6 have good avalanche properties for the plaintext and key. They are very close to the SAC (Strict Avalanche Criterion). The cipher texts of Rijndael and RC6 have good randomness and unpredictability from the results of runs test. However, the encryption speed of RC6 algorithm is much faster than that of Rijndael algorithm in the same experimental conditions, and is independent of the key length. The encryption and decryption speed of Rijndael are asymmetric although Rijndael algorithm is a symmetric block cipher. Meanwhile, RC6 needs more CPU and memory resources than Rijndael algorithm. So the use of RC6 is beneficial where high encryption speed is required while Rijndael is beneficial where memory resource is key concern.